Employee Benefits - Pension Plan Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 84,585	$ 93,486
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,371	5,073
Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	27,054	26,726
Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,421	3,728
Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	50,739	57,085
International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		874
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	81,214	88,413
Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 1 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	27,054	26,726
Level 1 | Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,421	3,728
Level 1 | Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	50,739	57,085
Level 1 | International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		874
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,371	5,073
Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	3,371	5,073
Level 2 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 | Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 | Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 | International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Equity Index Mutual Funds-International
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 | Domestic Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 0	0
Level 3 | International Individual Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value		$ 0